测量高压差分探头1 MHz共模抑制比窄带放大器的研制

Development of narrow-band amplifier for 1 MHz CMRR measurement of high-voltage differential probe

为了完整测量高压差分探头共模抑制比性能,需测量其50Hz^1MHz频率处的共模抑制比值。由于标准信号源的输出电平能力随着输出频率的升高而不断减小,1MHz时仅为20V左右,经过差分探头的衰减及共模抑制作用,使差分探头1MHz时共模输出信号电平极小,无法利用示波器进行测量。故研制了一台中心频率为1MHz的窄带放大器,该窄带放大器由低噪声高带宽放大单元和谐振选频单元组成,试验结果表明了其在输入电平50μV^1mV范围内的增益线性度优于±0.5dB,适用于差分探头1MHz频率处共模抑制比的测量。

In order to completely test the CMRR performance of high-voltage differential probe,it is required to measure the CMRR from 50 Hz to 1 MHz. When the standard signal source output frequency rose to 1 MHz, its output level ability decreased sharply. The output level of the standard signal source is about 20 V at 1 MHz. The common mode output signal is too weak to be measured on the oscilloscope due to the attenuation and common-mode rejection action of differential probe. This paper developed narrow band amplifier with center frequency 1 MHz. The narrow-band amplifier is constitutive of low noise high-bandwidth amplification unit and resonance frequency selective unit. The gain linearity of the narrow-band amplifier is better than ±0.5 dB in the input level from 50 μV to 1 inV. The testing results show that the narrow-band amplifier could be applied for 1 MHz CMRR measurement of high-voltage differential probe.